Could your symptoms point to a common deficiency?

The most commonly reported signs of Vitamin D deficiency include fatigue, bone pain, muscle weakness, muscle cramps, joint pain, low mood or depression, impaired wound healing, frequent infections, hair loss, back pain, brain fog, sleep disruption, weight gain, and anxiety. Not all will appear in every deficient individual, and many overlap with other conditions entirely unrelated to Vitamin D. The NHS and SACN report that 29-39% of UK adults fall below the deficiency threshold during winter and spring. A blood test measuring 25-hydroxyvitamin D is the only reliable way to confirm whether Vitamin D is the cause. (Source: NDNS; SACN 2016; NHS.uk)

Iron deficiency is the most strongly supported cause of hair loss in clinical literature. When ferritin drops below approximately 30 micrograms per litre, hair shedding often increases noticeably, even without full anaemia. B12 and Folate deficiencies impair red blood cell production, reducing oxygen delivery to follicles and triggering diffuse thinning. Vitamin D receptors are present in hair follicles and play a role in cycling, though the clinical evidence for D-related hair loss is less definitive than for iron. If you are losing hair and also experiencing fatigue, a blood panel covering ferritin, B12, folate, and Vitamin D is a reasonable first step. (Source: NDNS; clinical review literature)

The NHS and SACN recommend that all UK adults consider taking a daily Vitamin D supplement of 10 micrograms (400 IU) during autumn and winter (October to March). For people who spend very little time outdoors, have darker skin tones, or cover most of their skin, the recommendation extends to year-round supplementation. This guidance was strengthened following the SACN 2016 Vitamin D and Health report. Vitamin D toxicity from supplementation at recommended doses is extremely rare. Doses above 100 micrograms (4,000 IU) daily should not be taken without medical supervision. (Source: NHS.uk; SACN Vitamin D and Health Report 2016)

Vitamin B12 is found almost exclusively in animal-derived foods: meat, fish, dairy, and eggs. There is no reliable plant-based source in quantities sufficient to maintain adequate levels. The Pawlak et al. 2014 meta-analysis found that 52-86% of long-term vegans who do not supplement are B12 deficient. B12 deficiency develops slowly because the liver stores several years' supply, so a newly vegan person may not notice symptoms for 2 to 5 years. By the time neurological symptoms appear (tingling, numbness, balance problems, cognitive changes), some nerve damage may be irreversible. The British Dietetic Association and the Vegan Society both explicitly recommend that all vegans take a B12 supplement daily. (Source: Pawlak R et al. European Journal of Clinical Nutrition. 2014;68:541-548)

Beyond the well-known fatigue and bone pain, Vitamin D deficiency has been linked to several symptoms people do not typically associate with a vitamin. These include excessive sweating (particularly head sweating), a sensation of aching bones that feels like a deep bruise rather than a joint problem, frequent respiratory infections, slow wound healing, and pronounced low mood during winter. Some report a general heaviness in their limbs disproportionate to their activity level. Because Vitamin D plays a role in immune regulation, calcium metabolism, and mood-related neurotransmitter production, its deficiency can manifest in surprisingly diverse ways. If you are experiencing several of these symptoms persistently, a blood test measuring 25-hydroxyvitamin D is the only reliable way to confirm deficiency. (Source: NDNS; SACN 2016)

The most useful panel includes serum 25-hydroxyvitamin D (for Vitamin D status), serum B12, serum folate, serum ferritin (more informative than haemoglobin alone for iron stores), and full blood count (which can reveal macrocytic anaemia suggesting B12 or folate issues, or microcytic anaemia suggesting iron deficiency). Some GPs may not include all of these in a standard blood panel, so request them specifically and explain your symptoms. When interpreting results, be aware that normal ranges can be broad; you may experience symptoms at the lower end, particularly for ferritin and B12. Discuss borderline results with your doctor rather than dismissing them. (Source: NHS CKS; NICE guidance)

Yes. Several commonly prescribed medications impair B12 absorption. Metformin, widely used for type 2 diabetes, reduces B12 absorption in the ileum and is associated with B12 deficiency in up to 30% of long-term users. Proton pump inhibitors (PPIs) such as omeprazole and lansoprazole reduce stomach acid production, which is needed to release B12 from food. H2 receptor antagonists have a similar but milder effect. Long-term use of these medications without B12 monitoring is a recognised clinical risk. If you take metformin or PPIs regularly and have symptoms of B12 deficiency such as fatigue, tingling, or cognitive changes, ask your GP to check your B12 level at your next review. (Source: NICE CKS; NHS guidance on metformin)

Iron deficiency without anaemia is significantly more common than full iron deficiency anaemia and is frequently missed by standard blood tests that check only haemoglobin. The WHO estimates that for every person with iron deficiency anaemia, two to three more have depleted iron stores without reaching the anaemia threshold. In the UK, the NDNS found that 21% of women aged 19 to 64 had low iron stores, while only 5 to 8% had progressed to anaemia. Symptoms including fatigue, brain fog, exercise intolerance, and restless legs can appear well before haemoglobin drops. The key test is serum ferritin. If your symptoms suggest iron deficiency but your GP says your blood count is fine, specifically request a ferritin test. (Source: WHO; NDNS; NICE NG45)